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Coastal Storms, Coastal Nightmare
Major coastal storms are killers. Looking back on the human costs of Hurricane Harvey, which hit the coast of Texas in late August 2017, the Houston Chronicle memorialized the seventy-five people killed in the resulting flooding: "A beloved pastor and his wife swept away by a raging creek in Fort Bend County. An elderly man who died alone, trapped by rising waters in his west Houston home. Six members of the Saldivar family trying to escape the torrential rains. A dedicated police officer who could not ignore his duty. Those are among the many whom this storm took from us, and many others whose names we don't yet know."
Just a week later, Hurricane Irma, the strongest Atlantic basin hurricane ever recorded, devastated the Caribbean, the Florida Keys, and the western coast of Florida, resulting in the death of ninety-two people in the United States, including seventy-seven in Florida. The Florida Sun Sentinel interviewed a resident of Cudjoe Key: "It's been a nightmare. ... You live here in a resort, everything's nice and pretty, and the next day it's all gone. ... Death. That's what it sounded like to me." Winds exceeded 130 miles per hour and sea water surged five to eight feet above ground level in the Keys.
Then, less than a month later, on September 20, Hurricane Maria struck the island of Puerto Rico with winds of 155 miles per hour driving a surge of water six to nine feet high. The initial official death toll was sixty-four, but several organizations argued it was much higher. The New York Times reviewed differing estimates and found that 1,052 more people than usual died across the island in the forty-two days after the storm. A May 2018 report by researchers at Harvard University came to a much higher estimate, finding that 4,645 people died as a result of the hurricane. Many of these deaths are associated with lack of access to medical services or facilities or electric power. In August of 2018, the government of Puerto Rico settled on an estimate of 1,427 deaths directly due to storm damage while noting that estimates from other studies range between 800 and 8,000 deaths due to delayed health care.
The loss of life in these storms was tragic, but not record setting by American standards. The Galveston Hurricane in 1900 is thought to have killed between 6,000 and 12,000, with winds of over 140 miles per hour and a storm surge of fifteen feet. Hurricane Katrina killed at least 1,833 people in late August 2005, with wind speeds over 175 miles per hour and a storm surge of twenty-four to twenty-eight feet along the northern Gulf of Mexico. Hurricane Sandy brought high winds and a storm surge over nine feet at the lower end of Manhattan Island and along the New Jersey shore, claiming 106 lives, mostly from drowning, in October 2012. Roughly a dozen hurricanes have each resulted in over 100 deaths in the United States in the past century.
One factor behind the significant loss of life and damage costs of the 2017 storms is the growth of population and the value of assets along the coast. Another consideration is that the long-standing phenomena of major coastal storms is playing out against a backdrop of a warming planet. Climate models suggest that a warmer climate will result in more intense, and perhaps more frequent, coastal storms. In addition, warming temperatures are driving a gradual rise in sea levels globally and along the American coast. Rising seas will not make coastal storms more frequent or more severe but will push storm surges farther inland.
With these concerns in mind, it is worth looking more closely at the problem that connects coastal storms and rising seas: storm surge. It is also important to understand past trends in costs of major storms and how storms may change as the planet warms.
The Role of Storm Surge in Coastal Storm Deaths and Damage
A storm surge is a wave of ocean water, over and above the predicted astronomical tide, generated by high winds and low barometric pressure associated with a coastal storm. Smaller storms combine with high tides to generate nuisance flooding or, occasionally, flooding on the "coastal flood warning" scale of several feet.
A key thing about storm surges is that the bigger the storm — the greater the winds and lower the barometric pressure — the bigger the storm surge (see fig. 1–4). Exceptionally high storm surges, such as the twenty-four to twenty-eight feet delivered by Hurricane Katrina, have occurred, but surges of five to ten feet are more common, and damages can vary widely based on the elevation of the coast. Hurricane Michael, with the third lowest barometric pressure recorded at landfall, came ashore on the Florida Panhandle with storm surges in excess of ten feet east of Panama City and fourteen feet in Mexico Beach.
The other key thing to know about storm surges is that they are by far the deadliest element of a coastal storm. In 2014, Edward Rappaport of the National Hurricane Center published a paper looking at deaths from major storms over the past fifty years finding that, "roughly 90% of the deaths occurred in water-related incidents, most by drowning ..." and "storm surge was responsible for about half of the fatalities (49%)." In contrast, high winds were estimated to have caused less than 10 percent of deaths.
Given the deadly effect of storm surges, it is very useful to know what land areas are at risk of flooding by a surge in the event of a storm. Fortunately, understanding of coastal areas at risk of storm surges has improved significantly in recent years. The National Hurricane Center within the National Oceanic and Atmospheric Administration (NOAA) uses a model to "estimate storm surge heights resulting from historical, hypothetical, or predicted hurricanes." The "Sea, Lake and Overland Surges from Hurricanes" model, or SLOSH for short, predicts for each basin along the Atlantic and Gulf of Mexico coasts the geographic extent and depth of storm surge in the event of a given storm size (e.g., hurricane Categories 1–5).
Drawing on the SLOSH model and other data, NOAA estimates that, "in a worst-case scenario, approximately 24 million people along the East and Gulf coasts are at risk from storm surge flooding." The risk consulting company CoreLogic came to a roughly comparable conclusion in a 2018 report finding 6.9 million homes at risk of storm surge. NOAA found that by far the greatest number of people at risk of storm surge are in Florida, with significant populations at risk in Louisiana, New York, and New Jersey. These estimates of populations at risk of storm surge, however, are based on the land areas at risk with current sea level and do not reflect additional land area or population at risk based on future sea level, or more severe coastal storms, or growing coastal populations.
Knowing the coastal land areas most at risk of storm surge flooding in the event of a storm is a big step forward, but it would be even better to also have a sense of the risk of a major storm occurring at a specific place along the coast. The National Hurricane Center has data on that as well. This data is framed to provide a return period for major storms (i.e., hurricanes on the scale of Category 1–5) in a given coastal county, based on past experience, for the Atlantic Coast and the Gulf of Mexico.
For example, looking at NOAA's Hurricane Strike Frequency Map, it is possible to find that Miami–Dade County, Florida, has experienced six Category 1 hurricanes, and that a storm of that scale can be expected about eighteen times over an extended period (e.g., 1900–2009) (see table 1–1). Because these data are drawn from past experience, it does not reflect projected increases in storm intensity due to a warming planet.
Even with these impressive statistics, however, it is impossible to know from year to year when or where a major coastal storm will form or strike. Predictions of the path and intensity of hurricanes already formed, however, are getting better, thanks to NOAA's Hurricane Forecast Improvement Project. Started in 2009, the ten-year effort is intended to reduce errors in storm track and intensity estimates by 50 percent and extend forecasts from five to seven days.
Past Trends in Coastal Storms
Every four years, the United States Global Change Research Program, made up of scientists from federal agencies and other organizations, publishes a national assessment of changes in the climate. The 2014 National Climate Assessment, speaks to the subject of past coastal storms: "The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s." The 2017 Climate Science Special Report, which is part 1 of the 2018 National Climate Assessment, linked these storm changes to human activity: "Human activities have contributed substantially to observed ocean — atmosphere variability in the Atlantic Ocean (medium confidence), and these changes have contributed to the observed upward trend in North Atlantic hurricane activity since the 1970s (medium confidence)."
Exploring the question of trends in the costs of past major coastal storms, NOAA looked at a subset of all disasters costing over a billion dollars and found steady cost increases. In 2019, NOAA concluded that, since 1980, the United States has sustained 241 weather and climate disasters where overall damages and costs reached or exceeded $1 billion (including Consumer Price Index adjustment to 2018). The total cost of these 241 events exceeds $1.6 trillion. The trend, however, is upward. From 1980 to 2013, about a half a dozen billion-dollar disasters occurred each year while in the last five years the number has increased to about a dozen.
More important, NOAA evaluated costs of different types of disasters and found that hurricanes and related storms were the single largest type of disaster event: "In short, tropical cyclones are the most costly of the weather and climate disasters ... 40 tropical cyclones have caused a combined $862 billion in total damages — with an average of $21.6 billion per event. Accounting for just under a fifth (17 %) of the total number of events, tropical cyclones have caused almost half (55%) of the total damages attributed to billion-dollar weather and climate disasters since 1980." The average costs of other types of events NOAA evaluated include drought ($9.4 billion per event), flooding ($4.3 billion per event), and wildfires ($2.5 billion per event).
Average costs, however, can hide the fact that a single storm can cost over $100 billion. In January 2018, NOAA announced the final total cost of Hurricanes Harvey, Irma, and Maria to be a staggering $265 billion (Harvey, $125 billion; Irma, $50 billion; and Maria, $90 billion). As a point of reference, NOAA cites the cost of Hurricane Katrina as $161 billion (adjusted to 2017 dollars), and the cost of Hurricane Sandy as $71 billion (adjusted to 2017 dollars). Costs of the 2018 storms were more modest but still above average (i.e., $25 billion for Hurricane Michael and $24 billion for Hurricane Florence). The social and psychological costs of lost homes, disrupted lives, and broken communities, although significant, are not monetized.
In early 2019, the Congressional Budget Office (CBO) estimated that the country should expect annual economic losses of $54 billion due to hurricanes and tropical storms under current conditions and policies (i.e., not accounting for more severe storms or rising seas). Storm surge flooding of residential property generated the largest category of losses, followed by residential wind damage and flood and wind damage to commercial and public property.
As crushing as these costs of storm damages are for the communities and coastal property owners hit by a storm, much of the cost of recovering from major storms is now paid by federal taxpayers across the country. Costs to the federal government come in the form of losses by the National Flood Insurance Program and costs for disaster assistance, including billions of dollars in supplemental appropriations for the most damaging storms. CBO looked at expected annual costs to the federal government under current conditions and policies and estimated costs to be $17 billion, but these costs can be dramatically higher in the event of multiple major storms.
In addition to direct costs, major coastal storms also have more general economic impacts. Following Hurricane Harvey, the Wall Street Journal reported that "gasoline prices surged to a two-year high at the pump Thursday after the owner of the largest pipeline in the U.S. reported that shipments are being sharply curtailed, spreading the economic pain from Hurricane Harvey throughout the nation."
Anecdotal reports of broad economic impacts are generally confirmed by academic research. In a 2014 paper looking at the global record of economic impacts of tropical cyclones, Solomon M. Hsiang and Amir S. Jina came to a troubling conclusion: "We find robust evidence that national incomes decline, relative to their pre-disaster trend, and do not recover within twenty years. Both rich and poor countries exhibit this response. ... Income losses arise from a small but persistent suppression of annual growth rates spread across the fifteen years following disaster, generating large and significant cumulative effects."
Future Coastal Storms on a Warming Planet
Looking for long-term trends in the record of past coastal storms is one way to try to understand future storm patterns. Another approach is to develop models of changing climate conditions, such as air temperature and ocean condition, and estimate the frequency and severity of future storms. The science of "geophysical fluid dynamics" addresses the question of whether a warming planet will result in coastal storms that are more frequent or severe than those experienced today or in the past.
Use of models to project future coastal storms is a tricky business. The 2014 National Climate Assessment evaluated multiple studies and concluded that, "by late this century, models, on average, project a slight decrease in the annual number of tropical cyclones, but an increase in the number of the strongest (Category 4 and 5) hurricanes. ... There is some uncertainty in this as the individual models do not always agree on the amount of projected change."
The 2017 Climate Science Special Report generally backed the earlier assessment: "Both theory and numerical modeling simulations generally indicate an increase in tropical cyclone (TC) intensity in a warmer world, and the models generally show an increase in the number of very intense TCs." Focusing in on the Atlantic Basin, NOAA concluded that "it is likely that climate warming will cause Atlantic hurricanes in the coming century to have higher rainfall rates than present-day hurricanes, and medium confidence that they will be more intense (higher peak winds and lower central pressures) on average," and "it's likely the number of major hurricanes (Category 3 and higher) would increase by two in a similar active year at the end of century." Of course, more intense storms generate larger storm surges that reach higher elevations and farther inland than surges from less intense storms.
To make matters worse, more intense storms can increase rainfall, and the extent of coastal inundation, beyond the flooding that would result from just storm surge. The 2014 National Climate Assessment concluded that warmer air results in greater rainfall from hurricanes, finding that "almost all existing studies project greater rainfall rates in hurricanes in a warmer climate, with projected increases of about 20% averaged near the center of hurricanes." In September 2018, researchers at Stony Brook University evaluated the impact of Hurricane Florence, which deluged the Carolinas in 2018, reporting that "rainfall amounts over the Carolinas are increased by over 50% due to climate change."
This more intense rainfall might be manageable if greater storm intensity also resulted in storms passing over a given place faster. Unfortunately, these more intense storms are slowing down, raining on a given place longer. In a study that evaluated hurricanes between 1949 and 2016, James Kossin reported that hurricanes around the globe are moving more slowly; up to 10 percent slower globally, and as much as 20 percent slower when over land in the Atlantic region.
The stalling of Hurricane Harvey over Houston, which produced over four feet of rain in some locations, is an example of this storm-slowing effect. The extreme rainfall from Harvey is also considered a preview of future storm rainfall. Although some observers dismissed any role for climate change, an international team of scientists looked at data from Harvey and prior storms finding that, "global warming made the precipitation about 15% (8%–19%) more intense, or equivalently made such an event three (1.5–5) times more likely. This analysis makes clear that extreme rainfall events along the Gulf Coast are on the rise."(Continues…)
Excerpted from "A New Coast"
Copyright © 2019 Jeffrey Peterson.
Excerpted by permission of ISLAND PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Part I A Warming Climate Drives Coastal Storms and Rising Seas 7
Chapter 1 Coastal Storms, Coastal Nightmare 9
Chapter 2 Sea Level Rise Projections: Trending Upward 21
Chapter 3 Measuring a Shifting Coast 33
Part II Storms and Rising Seas Disrupt the American Coast 43
Chapter 4 Scale and Cost of the Coming Coastal Inundation 45
Chapter 5 Coastal Storm and Sea Level Rise Risks to Critical Infrastructure 57
Chapter 6 Coastal Ecosystems Facing Inundation: Wetlands, and Beaches 71
Chapter 7 Private Sector Losses as Seas Rise: Tourism, Fishing, and Energy 81
Part III A Nation Unprepared for Coastal Storms and Rising Seas 97
Chapter 8 The Politics of Coastal Storms and Rising Seas 99
Chapter 9 National Flood Insurance Program: Coastal Misdirection 113
Chapter 10 Coastal Disaster Planning: Preparing for the Wrong Hazards 127
Chapter 11 Coastal Management Programs: Overcommitted and Underfunded 137
Chapter 12 National Planning for Climate Change: An Answer to Coastal Inundation? 147
Part IV States, Communities, and Businesses Cope with Coastal Storms and Rising Seas 161
Chapter 13 Novel Challenges of Storms and Rising Seas 163
Chapter 14 State and Community Choices in Preparing for a Changing Coast 173
Chapter 15 Relocation: Often the Inevitable Choice 203
Chapter 16 Social and Psychological Dimensions of Coastal Storms and Rising Seas 227
Chapter 17 Business Community Response to Coastal Risks 237
Part V Campaign for a New Coast 259
Chapter 18 Framework for a National Storm and Sea Level Rise Program 261
Chapter 19 Funding Coastal Storm and Sea Level Rise Preparedness 289
Chapter 20 Campaign for a New Coast 301